WHILE the concept of dusting off the Brit vs. Yank rivalry was hardly revolutionary, the battle of the bands Friday at Madison Square Garden between Billy Joel and Elton John offered the sold-out house loads of thrills and even a few spills.

The smart money was on Elton John, the gap-toothed queen of England, to be the night’s top dog. He strutted into the Garden wearing aquamarine silks, ready to bury overweight Billy Joel, who not only looked too round to pound but was laid low by a cold that had forced him to cancel a gig in the Sunshine State earlier in the week.

The very healthy, 31/2-hour show was structured with a shared introduction, then separate (full) concert sets and a shared encore.

In their intro, which stitched “Your Song,” “Just the Way You Are” and “Don’t Let the Sun Go Down on Me” together, John was totally on the money vocally and in his work at the ivories. Joel croaked and wrung his hands as if they were so sweaty he was gonna slip off the piano.

Joel coughed, he said “it’s just a little cold – that don’t stop us here” and he even made a little joke by placing emphasis on the line “I love you, that’s forever” during “Just the Way You Are,” a tune he wrote for his first ex-wife. But despite his trouper’s the-show-must-go-on attitude, the guy seemed pretty messed up.

John confirmed it at the start of his solo set, expressing his gratitude for Joel’s effort and revealing that “Billy really is sick.”

He then ignited a set that actually made people wonder if Joel was going to come back at all.

There were the signature songs like “Philadelphia Freedom,” “Rocketman,” “Crocodile Rock” and “Levon” all of which had the expected audience approval.

Yet it was in the syncopated rocker “Take Me to the Pilot” where John pulled out all the stops and took the concert to the next level. The guy hammered at the piano with sharp, open-handed blows as if to remind us it really is a percussion instrument.

You could be Fats Domino, Jerry Lee Lewis, or even Joe Steinway, but Elton’s set would have given you pianist envy. It would have been a tough act to follow had Billy been in tip-top shape.

The break while Elton played served Billy’s voice well. When he opened his set with “Scenes From an Italian Restaurant,” if the Long Island native hadn’t alerted us that he was sick, it may have gone unnoticed. Energy, momentum and being in the Garden helped Joel defy gravity for a while.

He killed during “Moving Out,” was fiery for “Angry Young Man” and was just plain wonderful for “New York State of Mind,” which he cleverly segued into George Gershwin’s famous New York homage “Rhapsody in Blue.” Still, by the time Joel finished his set with “Only the Good Die Young,” you could count his voice among the casualties.

In the end, Elton was terrific and did win the battle, but Joel, as croaky and hurt as he was, won the war with the underdog’s spirit of trying just a bit harder and giving the fans more than he or anyone thought he had.